DOM is undefined when a session is created without a url parameter

[poftadeh]

Describe the bug
If no url is provided when creating a session, the dom object within a Browser class does not get initialized.

To Reproduce
POST to /session/ with the following capabilities:

{    
	"capabilities": {
      "firstMatch": [
        {
          "browserName": "pluma",
          "plm:plumaOptions": { "runScripts": false }
        }
      ]
    }
}

Describe the results you received:
this.dom is undefined.

Describe the results you expected:
this.dom to be set to a default jsdom object.

Additional context
Suspected cause is in Browser.ts:

      this.dom = await new JSDOM(' ', {
        resources: config.resourceLoader,
        runScripts: config.runScripts,
        beforeParse: config.beforeParse,
        pretendToBeVisual: true,
        cookieJar: config.jar
      });

await on a non-promise may be preventing the value from being set.